Text entry for mobile and handheld devices represents a field that is developing at a very fast pace. With the continuously decreasing size of PDA's and other devices, the main challenge of text entry has been the need for a compact keyboard area that does not compromise on the input speed or accuracy of the system. Devices that have built-in hardware keyboards do not allow for fast text input, since the keys on the keyboard are very small. Hand-writing recognition systems are highly dependent on the input quality and do not provide the desired level of speed and accuracy. In systems such as the Palm Pilot (developed by Palm Inc., Santa Clara Calif.), the user must first learn a unique alphabet, and even once this is mastered, the input speed is highly limited.
The use of keyboards having multiple characters on each key, for reducing the overall size of the keyboard, is known. U.S. Pat. No. 6,307,549 to King et al., hereby incorporated by reference, relates to a reduced keyboard disambiguating system having a keyboard with a reduced number of keys. A plurality of letters and symbols are assigned to a set of data keys so that keystrokes entered by a user are ambiguous. Due to the ambiguity in each keystroke, an entered keystroke sequence could match a number of words with the same number of letters. The disambiguating system includes a memory having a number of vocabulary modules. The vocabulary modules contain a library of objects that are each associated with a keystroke sequence. Each object is also associated with a frequency of use. Objects within the vocabulary modules that match the entered keystroke sequence are identified by the disambiguating system. Objects associated with a keystroke sequence that match the entered keystroke sequence are displayed to the user in a selection list. The main drawback to this invention is that it is mainly suitable for use for a telephone keypad. For use in other hand-held and mobile electronic devices, the input speed is too limited for the system to work effectively and the accuracy of the system is relatively low (for example, see Bohan (Bohan, M., Phipps, C. A., Chaparro, A., & Halcomb, C. G. (1999). A psychophysical comparison of two stylus-driven soft keyboards. Proceedings of Graphics Interface '99, 92–97. Toronto: Canadian Information Processing Society), disclosing a virtual keyboard adaptation for PDA's which was found to be slower than the QWERTY layout).
Other known systems employ a virtual keyboard, in which the user slides a stylus or other input device from one letter to the next in order to form a word. Quickwriting (Perlin K., “Quickwriting: Continuous Stylus-Based Text Entry”. Proc. ACM UIST, Tech. Note. 1998) uses such a sliding motion, but is limited in its capabilities because it requires that the stylus be returned to the center of the keyboard after each letter is inputted. Thus, producing a single word can be complex. Niemeier, in U.S. Pat. No. 5,574,482, hereby incorporated by reference, also uses a sliding motion for text input mainly for word prediction. Once a letter has been recognized, the system generates additional temporary keys based on the predicted next letter, in order to reduce the input time.
The Cirrin keyboard system (Mankoff, J. and G. D. Abowd. Cirrin: a word-level unistroke keyboard for pen input. Proc. ACM UIST, Tech. Note. 1998. p. 213–214.), (see FIG. 1G) uses a sliding motion on a annulus keyboard that is composed of 26 letters. At the end of the word, the stylus is lifted and a space is automatically created. Cirrin operates at a word level, and it does not require a dictionary. However, Cirrin is very slow, because the annulus circumference is large (26 letters) and because after each letter (or in some cases, series of letters), the stylus has to leave the annulus area so that the inputted character can be identified.
MessageEase (www.exideas.com) uses a nine-key keyboard. Disambiguation of words is obtained by a small sliding inside the key area in order to determinate the selected character. A nine-key text entry method allows for the selection characters by moving a cursor, though this method is not very fast because it requires two keystrokes for certain letters. Other text entry systems that have been developed are described in the following article, which is hereby incorporated by reference:
MacKenzie, I. S., & Soukoreff, R. W. (2002) “Text Entry for Mobile Computing: Models and Methods, Theory and Practice”. Human-Computer Interaction, 17, 147–198.
The idea of using sliding motion to generate a trajectory, which allows for the recognition of the inputted word, was described in U.S. Provisional Patent Application 60/430,33 (November 2002) (to the inventor of the present invention), to which the present application claims priority. More recently, a similar idea was set forth (Zhai, S., & Kristensson P., (April 2003) “Shorthand Writing on Stylus Keyboard”). In this system, a pattern dictionary of the 100 most common English words is generated from the ATOMIK keyboard, and users learn the shorthand symbol corresponding to each of those words according to its movement pattern on the keyboard. In order to maximize input speed, this method is designed to recognize patterns independently of location and scaling. The authors do not, however, employ the possibility to tracing patterns directly from the ATOMIK keyboard layout, because, using their system, this would require too much visual attention, thus resulting in a slower text input time. This remark will not apply for some preferred embodiments of the invention, as it will be clearly shown in the following sections.